This application is related to photovoltaic (PV) installation, in particular a PV system used with composition roof shingles.
Roof shingles are commonly used to cover roofing surfaces. The roof shingles are typically flat rectangular elements mounted to the roofing surface starting at the lower edge of the roof. The shingles arranged in rows with the side edges of the shingles of each row adjacent one another. The shingles are commonly nailed to the roofing surface along the upper edges of the shingles. Each additional row overlaps about one third of the lower row thus covering the nails.
Shingles have been made from many different types of materials. Some of the materials are relatively rigid, such as wood, metal, slate, asbestos-cement or ceramic. Other materials used for shingles are somewhat flexible; the most common of these are composition shingles, commonly referred to as asphalt shingles. Composition shingles are typically made of fiberglass, asphalt and aggregate. Laminated composition shingles are typically made of multiple layers of material, usually arranged for an aesthetically pleasing look.
Conventional PV systems on composition shingle roofs typically consist of rigid, aluminum framed PV modules attached to mounting systems which are in turn structurally secured to the roof. This leads to challenges in waterproofing (requiring separate flashing systems), aesthetics (systems attached to or above roofs inevitably appear to not belong there), and cost. In addition, they require specialized skills to install.
Some building-integrated products solve many of these problems with other roof types; but asphalt shingle roofs are particularly difficult because the roof coverings are quite thin (around ¾″ maximum stack height). This limits the available depth to achieve structural rigidity of the PV module, ventilation, and space for wiring. Also, PV modules tend to become more costly on a per-watt basis as their physical size becomes smaller. Because the shingle sheets of asphalt shingle are relatively small, using the same form factor for the PV module is expensive. One known attempt to produce a module that integrates cleanly with asphalt shingles is the Uni-Solar solar shingle, model SHR-17, from United Solar Ovonic LLC of Auburn Hills, Mich. This solar shingle is used to replace a portion of a single row of shingles. One example of this product has a length of 86.4 inches and a height of 12 inches. The active PV area occupies less than 50% of the surface. Therefore, it also has a relatively small form factor compared to conventional PV modules. In addition, because the photovoltaic portion of a conventional solar shingle is attached directly to the roofing surface, there is nowhere to run wiring. Thus many holes must be drilled in the waterproofing felt and roof deck and wiring completed in the attic. This requires a large amount of labor and compromises the waterproofing integrity of the roof. Also this configuration does not allow for any backside ventilation of the module, leading to high operating temperatures.